President Reagan presented National Medals of Science to 19 winners yesterday, telling them that they have made "an outstanding contribution to our way of life and our future."

At an East Room ceremony, Reagan said, "there's no nation on Earth that can match our scientific capability, our standard of living and our national security."

The medals went to:

Howard L. Bachrach, retired from the Agriculture Department at Plum Island, N.Y., for pioneering research in molecular virology.

Paul Berg of Stanford University for understanding the mechanisms of gene expression.

Wendell L. Roelofs of Cornell University for his fundamental contribution to basic and applied biology in the field of insects.

Berta Scharrer, emeritus professor at Albert Einstein College, for pioneering contributions in establishing the concept of neurosecretion.

Roald Hoffmann of Cornell University for his creative applications of theory to organic and inorganic chemistry.

George C. Pimentel of the University of California at Berkeley, for his varied and ingenius use of infrared spectroscopy to study chemical bonding and molecular dynamics.

Richard N. Zare of Stanford University for his seminal contributions to molecular spectroscopy, photochemistry and chemical reaction dynamics.

William R. Hewlett, vice chairman of Hewlett-Packard Co., for pioneering accomplishments in the creation and manufacturing of electonic instruments.

George M. Low, the late president of Rensselaer Polytechnic Institute, for major and lasting contributions to manned space flight.

The late John G. Trump of Massachusetts Institute of Technology for his introduction of new machines and methods for widespread beneficial application of ionizing radiation to medicine.

Herman H. Goldstine, executive officer of the American Philosophical Society in Philadelphia, for his funadamental contributions to the development of the digital computer, computer programming and numerical analysis.

I.M. Singer of Massachusetts Institute of Technology for his inspired revival of differential geometry and its connection to analysis.

E. Margaret Burbidge of the University of California at San Diego for leadership in observational astronomy.

Maurice Goldhaber of the Brookhaven National Laboratory for his contributions to nuclear physics.

Helmut E. Landsberg, emeritus professor at the University of Maryland, in recognition of his outstanding contributions to the advancement of knowledge and applications of climatology.

Walter H. Munk of the University of California at San Diego for his contributions to geophysics and physical oceanography.

Frederick Reines of the University of California at Irvine for his experimental discovery of the free neutrino and the elucidation of its properties and interactions.

Bruno B. Rossi of Massachusetts Institute of Technology for fundamental contributions to physics and astronomy through his investigations into nature and origin of cosmic rays.

J. Robert Schrieffer of the University of California at Santa Barbara in recognition of his insight into cooperative effects in solids and solid surfaces.